Steerable catheter having steering fins

ABSTRACT

A lumen wall of a blood vessel, such as a coronary artery, is imaged by inserting a catheter into the vessel and emitting near-IR radiation toward the lumen wall through a side window formed in the catheter. Blood flowing through the vessel is caused to react with a fin arrangement formed on a body of the catheter to displace the window toward a region of the lumen wall opposing the window in order to minimize the amount of blood that is interposed between the window and the lumen wall. Thus, the amount of radiation that is scattered or absorbed by the blood is minimized.

This application is a continuation of patent application Ser. No.09/977,948 filed on Oct. 17, 2001, now U.S. Pat. No. 6,658,278.

BACKGROUND OF THE INVENTION

The present invention relates to the use of catheters in performinginfrared imaging to inspect and characterize the lumen of a bloodvessel, especially a coronary artery.

Visual imaging of internal body structures has heretofore been performedin certain medical procedures. For example, visual imaging by means ofendoscopes introduced into the body has been useful in guiding themovements of certain medical devices inserted into the body for bodytreatment, and to view the results.

It is necessary that the body region in which the visual imaging, orendoscopy, is to be performed, contain a fluid that is transparent tothe light wavelengths being utilized. Thus, visual imaging within bodycavities such as the stomach can be performed after evacuating thestomach.

A form of endoscopy, called angioscopy, has been performed in coronaryarteries. However, substances in the blood can obscure the image. Forexample, light can be scattered by red blood cells and absorbed byhemoglobin in the blood. Accordingly, it has been required that bloodfirst be removed from the arterial region being inspected, and replacedwith a clear saline solution which is transparent to the lightwavelength. Difficulties such as this in obtaining a clear image havelimited the usefulness of visual imaging of blood vessels.

The imaging of internal body cavities has also been performed by sensinginfrared radiation emitted from body structures (see U.S. Pat. Nos.5,445,157 and 6,178,346). In U.S. Pat. No. 6,178,346 for example, it hasbeen proposed to inspect the lumen of a coronary artery by introducinginto the artery a catheter which emits infrared light toward the wall ofthe lumen. Light that is reflected from the lumen wall is directed to aninfrared camera so that a real-time image of the lumen wall can beformed. Such a procedure enables physicians to identify potentiallydangerous plaque build-up and lesions on the lumen wall, andspecifically identify characteristics of vulnerable plaque in the lumenwall intima.

It would be desirable to provide improved methods and apparatus forimaging a lumen of a blood vessel, such as a coronary artery using lightof any suitable wavelength, intensity and duration, chosen independentlyof the light-absorption and light-scattering characteristics of blood.

It would also be desirable to provide such methods and apparatus whichcan utilize relatively low intensity light in the near infrared region,especially 0.8 to 1.4 microns.

SUMMARY OF THE INVENTION

The present invention relates to a catheter for imaging a lumen of ablood vessel, such as a coronary artery. A catheter includes a catheterbody which has a lateral window adjacent a tip of the body. A fiberoptic cable is disposed in the body for transmitting light. An opticalhead is disposed adjacent the window for transmitting the light throughthe window and toward a wall of the lumen and for receiving reflectedlight from the lumen wall and transmitting the received reflective lightto the cable. A deflector arrangement is disposed on a external surfaceof the catheter body adjacent the window for interacting with a flow ofblood through the vessel to displace the window laterally toward aregion of the lumen wall opposing the window, to minimize the amount ofblood disposed between the window and the lumen wall.

The invention also pertains to a method of imaging a wall of a lumen ofa blood vessel. The method comprises the steps of:

A) inserting a catheter body into the vessel;

B) emitting radiation through a side window formed in an outer peripheryof the body;

C) receiving radiation reflected off the lumen wall and transmitting theradiation to imaging equipment; and

D) causing a deflector arrangement on the body to react with bloodflowing through the vessel to displace the window toward a region of thelumen wall opposing the window to thereby minimizing the amount of blooddisposed between the window and the lumen wall.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The objects and advantages of the invention will become apparent fromthe following detailed description of preferred embodiments thereof inconnection with the accompanying drawings in which like numeralsdesignate like elements and in which:

FIG. 1 is a side elevational view of a front end of a catheter accordingto the present invention;

FIG. 2 is a view similar to FIG. 1, but taken at a location spaced 90degrees from that of FIG. 1, and with a portion of the catheter wallbroken away;

FIG. 3 is a front end view of the catheter of FIG. 1;

FIG. 4 is a front perspective view of the catheter emerging from asheath;

FIG. 5 is a rear perspective view of the catheter of FIG. 1;

FIG. 6 is a schematic view depicting the manner of operation of thecatheter in a blood vessel; and

FIG. 7 is a view similar to FIG. 2 of a modified catheter.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Depicted in FIGS. 1-5 is an infrared endoscope catheter 10 according tothe present invention. The catheter 10 is similar to a conventionalvisible-region endoscope in that it includes a tubular body 12containing an optical head 14, and a fiber optic cable 16. The cable 16transmits IR (infrared) radiation from an IR source to the optical head,and then transmitting away from the optical head the IR radiation thathas been reflected from the wall W of a human body part, in this case alumen of a blood vessel, such as a coronary artery lumen (see FIG. 6).The optic head comprises a conventional lens arrangement for emittingthe IR radiation (preferably near-IR radiation) laterally from thecatheter through a side window 18 disposed in a front portion of thebody 12. After being reflected from the lumen wall, the near-IRradiation is received by the lens arrangement and transmitted out of thecatheter back through the fiber optic cable. That radiation is thentransmitted to a conventional infrared camera (not shown) and convertedto an electric signal that can be used to form an image in conventionalimage processing equipment (not shown).

As explained earlier, substances in the blood, especially red cells,hemoglobin can render the blood opaque to the near-IR radiation.Accordingly, the catheter 10 includes a deflector structure, preferablyan arrangement of fins 20, which deflector structure reacts with theforce of flowing blood to produce a resultant force which deflects theside window laterally toward the region of the lumen wall facing thewindow, thereby minimizing the amount of blood interposed between thewindow and the lumen wall. In other words, the resultant of all forcesacting on the deflector structure displaces the catheter laterallytoward the wall of the blood vessel.

The fin arrangement comprises diametrically opposite fins, preferablytwo diametrically opposite fin sets S1, S2, each set containing threefins 20. Each fin 20 is oriented obliquely relative to a longitudinalaxis A of the catheter, and thus obliquely relative to the direction ofblood flow BF (see FIG. 6). In particular, each fin is inclined in adirection such that the front end of each fin, i.e., the end closest tothe tip (front end) of the catheter, is directed toward the side of thecatheter opposite the side in which the window 18 is formed. As aresult, the blood flow will apply to each fin a force having an axiallyforward component F1, and a laterally outward component F2 directedtoward the region of the lumen wall facing the window 18. The componentF2 displaces the front portion of the catheter laterally toward thatregion of the lumen wall, as shown in FIG. 6.

The window 18 is situated on a portion of the outer circumference of thecatheter body that is spaced circumferentially from each set of fins byan angle ∝ of about ninety degrees as the catheter is viewed from theend (see FIG. 3). Thus, the window can closely approach the lumen wallwhen the front portion of the catheter is deflected toward the lumenwall (see FIG. 6). Consequently, the amount of blood situated betweenthe window 18 and the lumen wall is minimized to facilitate the abilityof the optical head 14 to transmit IR radiation toward the lumen walland receive the radiation that is reflected from that wall, i.e., thetendency for the radiation to be scattered or absorbed by substances inthe blood is minimized.

In practice, the catheter 10 is fed into the blood vessel through asheath 30 (FIG. 4) as is conventional. Due to force component F2generated as the blood flow acts against the fins 20, the front portionwindow 18 will be displaced laterally to the lumen wall. As imaging isperformed by the emission of near-IR radiation, the catheter is advancedand is rotated about its axis A to enable the entire inner circumferenceof the lumen wall to be inspected. In order to image the entire lumenwall, the window 18 should track the lumen wall during catheterrotation. When utilizing a catheter according to the present invention,the rate of rotation of the catheter should be slow enough to providesufficient time for the deflected front portion of the catheter to adaptto force changes applied to the fins during the catheter rotation andremain disposed at the lumen wall. The optimum speed of catheterrotation will vary, depending upon various factors such as the speed ofblood flow. Generally speaking, the rate of rotation should probably beless than 2 rps (revolutions per second) and possibly even as low as 0.5rps.

The number of fins and the orientation of the fins relative to thecatheter body and to each other can vary. It has been found for example,that two fins per set are preferable to one fin per set, and three finsper set are preferable to two fins per set. By varying the angle ofinclination between the fins and the axis A, as the catheter is viewedfrom the side (see FIG. 2), the magnitude of the force F2 can bealtered.

The shape of the catheter body may vary. For example, the tip of thecatheter body could be enlarged, rather than narrowed as shown.

The shape of the fins can vary. Instead of being flat, the fins could becurved, preferably to present a concave surface opposing the directionof blood flow BF.

A cowl could be wound around the circumference of the catheter body toencompass the fins in order to direct blood flow to the fins. This couldalso serve to protect the vessel lumen wall.

When inserted into a coronary artery, the catheter will be introducedfrom the sheath in the same direction as the blood flow BF. The speed ofthe blood flow is sufficiently great to generate a high enough force F2for deflecting the front portion of the catheter to the lumen wall W.Sufficient blood speed also exists in the aorta and the carotid arteriesto enable the catheter to be used there as well.

The catheter may be able to function in blood vessels where the bloodflow rate is significantly less, e.g., in veins, by displacing thecatheter through the vessel in a direction opposite the direction ofblood flow, thereby increasing the blood flow rate relative to the finsfor generating a higher force F2. Such a catheter 100 is depicted inFIG. 7. It will be appreciated that the orientation of the fins 120 mustbe altered from that of the fins 20 of the previously describedembodiment. That is, the fins 120 must be oriented such that the forwardend of each fin (i.e., the end closest to the tip of the catheter) isdirected toward the side of the catheter body in which the window isformed.

It will be appreciated that the present invention enables light of anysuitable wavelength, intensity and duration to be employed in imaging ablood vessel wall, with minimal risk of scattering and absorption.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without departing from the spiritand scope of the invention as defined in the appended claims.

1. A catheter insertable into a blood vessel and comprising: a body; adeflector arrangement projecting from an external surface of the bodyadjacent a front portion of the body for interacting with a flow ofblood through the blood vessel, wherein the resultant of all forcesacting on the deflector arrangement is directed to displace the catheterbody laterally toward a region of a wall of the vessel, to minimize anamount of blood disposed between the catheter body and the vessel wall;wherein the deflector arrangement comprises fins disposed on oppositesides of the catheter body and arranged to be displaced towards thevessel wall by the force of blood flow.
 2. The catheter according toclaim 1 wherein the fins are generally diametrically opposed on thecatheter body.
 3. The catheter according to claim 2 wherein there aretwo sets of diametrically opposed fins, each set comprising a pluralityof fins.
 4. The catheter according to claim 1 wherein each fin extendsin a direction inclined obliquely relative to a longitudinal axis of thecatheter body, as the catheter body is viewed from the side.
 5. Thecatheter according to claim 1 wherein all of the fins are oriented at anoblique angle relative to a longitudinal center axis of the catheterbody, and all fins are oriented to be displaced toward the same regionof the wall of the vessel by the force of blood flow.
 6. A catheterinsertable into a blood vessel and comprising: a body; a deflectorarrangement projecting from an external surface of the body of thecatheter adjacent a front portion of the body for interacting with aflow of blood through the blood vessel to displace the catheter bodylaterally toward a region of a wall of the vessel, to minimize an amountof blood disposed between the catheter body and the vessel wall; whereinthe deflector arrangement comprises fins disposed on opposite sides of asection of a center axis of the catheter body and arranged to bedisplaced towards the vessel wall by the force of blood flow, whereinthe fins are fixed against movement relative to the section of thecenter axis.